1. Field of the Invention
The present invention relates to a positive resist composition suitable for use in the ultramicrolithography process such as production of VLSI or high-capacity microchip or in other photofabrication processes, and a pattern forming method using the same. More specifically, the present invention relates to a positive resist composition capable of forming a high-resolution pattern by using KrF excimer laser light, electron beam, EUV light or the like, and a pattern forming method using the same. That is, the present invention relates to a positive resist composition suitably usable for fine processing of a semiconductor device, where KrF excimer laser light, electron beam or EUV light is used, and a pattern forming method using the same.
2. Description of the Related Art
In the process of producing a semiconductor device such as IC and LSI, fine processing by lithography using a photoresist composition has been conventionally performed. Recently, the integration degree of an integrated circuit is becoming higher and formation of an ultrafine pattern in the sub-micron or quarter-micron region is required. To cope with this requirement, the exposure wavelength also tends to become shorter, for example, from g line to i line or further to KrF excimer laser light. At present, other than the excimer laser light, development of lithography using electron beam, X ray or EUV light is proceeding.
In the lithography involving an ion injection step using KrF excimer laser light, it is also an important problem to satisfy high resolution, good defocus latitude depended on line pitch and the like all at the same time, and this problem needs to be solved.
In regard to the resist suitable for the lithography process used in the ion injection step, as described in JP-A-7-84364 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-7-316268, JP-A-7-319155, JP-A-10-186647, JP-A-2006-328241 and JP-A-2000-284482), studies are being made on a chemical amplification-type resist where light transmittance of the resist film is adjusted from the standpoint of controlling the resist pattern profile on a high-reflection substrate, and in the case of a positive resist, a chemical amplification-type resist composition comprising, as main components, a phenolic polymer insoluble or sparingly soluble in an alkali developer but becoming soluble in an alkali developer under the action of an acid (hereinafter, simply referred to as a “phenolic acid-decomposable resin), an acid generator, and a coloring matter for adjusting the light transmittance is supposed to be effective. There is also known a case where the coloring matter for adjusting the light transmittance is connected to a phenolic acid-decomposable resin. With respect to the coloring matter for adjusting the light transmittance, an anthracene structure, a benzenecarboxylic acid structure, a naphthalenecarboxylic acid structure, a thiophene structure and the like are known.
However, by any combination of these techniques, it is impossible at present to satisfy the performances in terms of high resolution, scumming, iso-dense bias and stationary wave reduction in the ultrafine region.